Popular

March 8, 2006

Lab Heats Particles to Temperatures Beyond the Sun

by Sam Savage

ALBUQUERQUE, N.M. -- A particle accelerator at Sandia National Laboratories has heated a swarm of charged particles to a record 2 billion degrees Kelvin, a temperature beyond that of a star's interior.

Scientists working with Sandia's Z machine said the feat also revealed a new phenomenon that could eventually make future nuclear fusion power plants smaller and cheaper to operate than if the plants relied on previously known physics.

"At first, we were disbelieving," said Chris Deeney, head of the project. "We repeated the experiment many times to make sure we had a true result and not an 'Ooops'!"

Sandia's experiment, which held up in tests and computer modeling in the 14 months since it was first done, was outlined in the Feb. 24 edition of Physical Review Letters. The authors also presented a theoretical explanation of what happened by Sandia consultant Malcolm Haines, a physicist at Imperial College in London.

The achievement will not mean fusion in the near future, but it's another step toward that goal, said Neal Singer, a Sandia spokesman.

Sandia's Z machine, housed in a warehouse-sized laboratory, is designed to generate tremendous amounts of energy. It normally passes 20 million amps of electrical current through a cluster of tungsten wires about the size of a spool of thread. The massive electrical pulse instantly vaporizes the wires into a cloud of charged, superhot particles known as plasma.

At the same time, the Z machine compresses the plasma in a powerful magnetic field. Almost instantly, the particles smash together in a collision that can emit temperatures in the millions of degrees.

Sandia boosted the Z machine's output into the billions of degrees in part by substituting steel wires around a larger, coffee cup-sized core. Increasing the size of the core increased the distance the ions traveled, giving them more time to gain velocity and therefore energy.

But the larger core did not account for all the heat generated in the collision. It also could not explain why the plasma particles did not stop moving once they collided with one another - for about 10 billionths of a second, some unknown energy caused them to keep pushing back against the magnetic field.

Haines theorized that the energy of the Z machine's magnetic field itself added energy to the particles.

The new phenomenon could be exploited in fusion power as a trigger that would set off a controlled nuclear reaction by heating a small amount of deuterium or tritium. It is likely to be more efficient than other proposed methods because it produces higher temperatures while requiring less input energy.